Preparation of carboxylic acids by carbonylation of alcohols

Abstract

Carboxylic acids having the structural formula R 1 COOH, wherein R 1 is a linear, branched or cyclic chain alkyl radical of from 1 to 6 carbon atoms or a Φ--C n H 2n -- radical wherein Φ is phenyl and 1≦n≦6, are prepared by carbonylating an alcohol having the formula R 1 --OH with carbon monoxide in liquid phase, in the presence of a catalytically effective amount of nickel and an alkyl or acyl halide promoter therefor, at a temperature of at least about 120° C. and under a total pressure of less than 200 bars, and said carbonylation being carried out in the presence of at least one chromium salt in which the chromium is in a state of oxidation (p) of greater than zero (p>0), and in an initial carboxylic acid reaction medium having the formula R 2 --COOH, wherein R 2 is defined as was R 1 above, and further wherein R 1 and R 2 may be the same or different.

What is claimed is: 
     
       1. A process for the preparation of a carboxylic acid having the structural formula R 1  COOH, wherein R 1  is a linear, branched or cyclic chain alkyl radical of from 1 to 6 carbon atoms or a Φ--C n  H 2n  -- radical wherein Φ is phenyl and 1≦n≦6, comprising carbonylating an alcohol having the formula R 1  --OH with carbon monoxide in liquid phase, in the presence of a catalytically effective amount of nickel and an alkyl or acyl halide promoter therefor, wherein said acyl halide is of the formula ##STR3## in which X represents a chlorine, bromine or iodine atom and R 3  is defined as was R 1  above, and further wherein R 3  and R 1  may be the same or different, and under a total pressure of less than 200 bars, said carbonylation being carried out in the presence of at least one chromium salt in which the chromium is in an oxidation state (p) of greater than zero (p>0), and in an initial carboxylic acid reaction medium having the formula R 2  --COOH, wherein R 2  is defined as was R 1  above, and further wherein R 1  and R 2  may be the same or different. 
     
     
       2. The process as defined in claim 1, wherein the alkyl or acyl halide is an iodide. 
     
     
       3. The process as defined by claim 2, wherein the halide is a C 1  -C 4  -alkyl iodide. 
     
     
       4. The process as defined by claim 3, wherein the alkyl iodide is methyl iodide. 
     
     
       5. The process as defined by any one of claims 1 to 4, wherein R 1  is a C 1  -C 4  -alkyl radical and R 2  is a linear, branched or cyclic chain C 1  -C 6  -alkyl radical or a Φ--C n  H 2n  -- radical, in which Φ is phenyl and 1≦n≦6. 
     
     
       6. The process as defined by claim 5, wherein R 1  is methyl. 
     
     
       7. The process as defined by claim 1, wherein the carboxylic acid R 2  COOH comprises at least 10% by volume of the initial reaction medium. 
     
     
       8. The process as defined by claim 7, wherein the concentration of nickel in the reaction medium ranges from 5 to 2,000 mg-atoms per liter. 
     
     
       9. The process as defined by claim 8, wherein said concentration of nickel ranges from 20 to 1,000 mg-atoms per liter of reaction medium. 
     
     
       10. The process as defined by claim 8, wherein the concentration of alkyl or acyl halide in the reaction medium ranges from 0.5 to 8 mols per liter. 
     
     
       11. The process as defined by claim 10, wherein said concentration of alkyl or acyl halide ranges from 0.8 to 6 mols per liter. 
     
     
       12. The process as defined by claim 1 or 10, wherein R 1  and R 2  are identical. 
     
     
       13. The process as defined by claim 12, wherein the chromium salt has the formula Cr n   p+  X q   m- , in which q is the ratio (n×p)/m, m is equal to 1, 2 or 3, p=2, 3, 4, or 6, n is 1 or 2 and is selected in accordance with the respective values of m and p such that q is an integer, and X m-  is OH - , Cl - , Br - , I - , O -- , PO 4 .sup..tbd., CH 3  COCHC(CH 3 )O - , HCOO - , C 2  O 4   -- , R 4  --COO - , R 4  --O - , NO 3   -  and CO 3   -- , R 4  being defined exactly as was R 1  and R 4  and R 1  may be the same or different. 
     
     
       14. The process as defined by claim 13, wherein p=3. 
     
     
       15. The process as defined by claim 13, wherein the anion (X m- ) is a carboxylate of the formula R 4  --COO -  in which R 4  is defined as was R 1 , and R 4  and R 1  may be the same or different. 
     
     
       16. The process as defined by claim 15, wherein the anion (X m- ) is acetate. 
     
     
       17. The process as defined by claim 13, wherein the atomic ratio Cr/Ni ranges from 0.1 to 200. 
     
     
       18. The process as defined by claim 17, wherein the ratio Cr/Ni ranges from 0.5 to 100. 
     
     
       19. The process as defined by claim 18, wherein the ratio Cr/Ni ranges from 1 to 50. 
     
     
       20. The process as defined by claim 1, wherein the reaction temperature is at least 120° C. 
     
     
       21. The process as defined by claim 20, wherein the reaction temperature ranges from 160° to 200° C. 
     
     
       22. The process as defined by claim 21, wherein the partial pressure of the carbon monoxide ranges from 10 to 100 bars.